Mapping particulate dust with phones

iSpex device on a smartphone. Image by Sebastiaan ter Burg , published under licence CC BY 2.0iSpex is a plastic contraption that can be clipped on top of a smartphone’s camera. In this simple slit spectrograph light is defracted and polarized by shining through birefringent plastic sheets and a polarisation film. iSpex measures how aerosoles – microscopic or nanoscopic particles hovering in the athmosphere – change the polarization of the highly polarized light that shines from an unclowded, blue sky. This change in polarization renders a distinct pattern in the spectrum, that is cast by the iSpex-device into the phone’s camera. By this approach, iSpex can measure how the air is polluted with particulate dust, which is regarded especially unhealthy and has become topic of fierce political discussions, when the EU ordered city governments to regulate and even lock out automotive traffic.

Over the course of summer and autumn 2013, thousands of people in the Netherlands participated in „national iSpex days“, jointly measuring particulate dust. The first results of this awesome social effort are published, and we can hope this project will find epigones in other countries.